"The certificate is invalid"

Hello,
Would someone please explain why I get all these "The certificate is 
invalid" errors for every page of my website at
https://ve3oat.ca
when checking them with the W3C mobile validator.

It is a Severe error and I am very concerned that it will affect 
visitors using mobile devices.  The pages all look fine on my own tablet 
and are not blocked.  My SSL certificate is valid, as far as I can tell.

Thanks for any help.
.... Martin

Received on Monday, 29 February 2016 22:52:13 UTC